Fibrous proteins

Fibrous proteins are proteins whose individual polypeptide-chain molecules adopt an overall elongated, ROD-like shape, rather than the compact sphere of a globular protein. This elongated shape results from multiple polypeptide chains being held closely PARALLEL to one another (rather than any single chain coiling in on itself), an arrangement stabilised chiefly by extensive hydrogen bonding and, in some fibrous proteins, by covalent disulfide bonds running between the parallel chains. Because their exterior surface is largely made of the non-polar, structural portions of the chains rather than an outward-facing polar surface, fibrous proteins are, as a class, generally INsoluble in water -- consistent with their typical biological role as tough, mechanically strong structural materials rather than mobile, functional molecules. Well-known ex …